The development of electrical, mechanical, biological and other devices has seen dramatic achievements in the implementation of ever-smaller objects and arrangements. In many applications, atomic, molecular or macromolecular arrangements having dimensional characteristics of a relatively small size (e.g., less than 100 nanometers) have seen increased development and implementation. These arrangements are often manufactured, manipulated or otherwise controlled on an atomic scale. Technological areas involving such small-scale objects are often referred to as those areas pertaining to nanotechnology.
One aspect of nanotechnologies that has been challenging relates to the ability to control and/or manipulate sub-micron (e.g., nanoscale) objects. For instance, isolating, orienting, translating or otherwise processing sub-micron objects for analysis and other purposes has been particularly challenging. Where small objects are in fluid solution such as a liquid or gas, Brownian motion of the objects (thermally-driven motion related to collisions of the objects with other molecules in solution) also poses problems to analyzing the objects. At room temperature, Brownian motion is quite large for small objects (mean square displacement per unit time scaling inversely with the diameter).
Previous approaches to manipulating small-scale objects have involved the use of laser tweezers, such as described in A. Ashkin, J. M. Dziedzic, J. E. Bjorkholm, and S. Chu, Observation of a Single-Beam Gradient Force Trap for Dielectric Particles, Opt. Lett. 11, 288 (1986). Magnetic tweezers have also been used to trap and manipulate micron-scale objects. See, e.g., C. Gosse and V. Croquette, “Magnetic tweezers: micromanipulation and force measurement at the molecular level,” Biophys. J. 82, 3314 (2002). Other approaches have involved AC dielectrophoresis, which have been used to trap micrometer-scale objects (see, e.g., P. R. C. Gascoyne and J. V. Vykoukal, Dielectrophoretic Concepts for Automated Diagnostic Instruments, Proc. IEEE 92, 22 (2004); J. Voldman, R. A. Braff, M. Toner, M. L. Gray, and M. A. Schmidt, Holding Forces of Single-Particle Dielectrophoretic Traps, Biophys. J. 80, 531 (2001); and T. B. Jones, Electromechanics of Particles, (Cambridge University Press, New York, 1995)).
While useful in certain aspects, trapping very small objects with the above (and other) previously-used approaches has been challenging. For example, with laser tweezers, magnetic tweezers and approaches based on dielectrophoresis, the maximum force available for trapping an object is generally proportional to the object's volume. In this regard, trapping sub-micron objects, and in particular, trapping objects much less than one micron in cross-section has been particularly challenging due to the scaling of the force available to trap such small objects. Moreover, for much smaller objects, heat-generating trapping approaches such as that associated with the laser power required to trap particles with laser tweezers can cause heating and photochemistry, both of which may disrupt the function of polymers or sensitive biological molecules such as delicate enzymes. Approaches based on magnetic interactions suffer from lack of generality, because the object to be trapped must be magnetic, and magnetic forces are generally small for all but a few materials, limiting the application of such approaches.
The above and other issues have presented challenges to the manipulation of small particles, and in particular to the manipulation and use of sub-micron objects.